<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <!-- enctype：multipart/form-data参数是二进制 -->
  <form action="/api/upload" method="post" enctype="multipart/form-data">
    <div>
      用户名：<input type="text" name="uid">
    </div>
    <div>
      头像:
      <button type="button" name="selectPic">请选择...</button>
      <input type="file" name="pic" multiple style="display: none;">
    </div>
    <div>
      照片：
      <input type="file" name="img" multiple>
    </div>
    <div>
      <button type="submit">提交</button>
    </div>
  </form>
</body>
<script>
  const form =document.forms[0];
  form.selectPic.onclick = function(){
    form.pic.click()
  }
  form.pic.onchange = function(){
    form.selectPic.innerHTML = this.value
  }
</script>
</html>